In general, an integrated circuit refers to an electrical circuit contained on a single monolithic chip containing active and passive circuit elements. As should be well understood in this art, integrated circuits are fabricated by diffusing and depositing successive layers of various materials in a preselected pattern on a substrate. The materials can include semiconductive materials such as silicon, conductive materials such as metals, and low dielectric materials such as silicon dioxide. The semiconductive materials contained in integrated circuit chips are used to form almost all of the ordinary electronic circuit elements, such as resistors, capacitors, diodes, and transistors.
Integrated circuits are used in great quantities in electronic devices such as digital computers because of their small size, low power consumption and high reliability. The complexity of integrated circuits ranges from simple logic gates and memory units to large arrays capable of complete video, audio and print data processing, including devices for operation in radio frequency (RF) applications. As the semiconductor industry strives to meet technological demands for faster and more efficient circuits, integrated circuit chips and assemblies are created with reduced dimensions, higher operating speeds and reduced energy requirements. As integrated circuit signal speeds increase, timing errors and pulse width deviations within such signals may constitute a greater portion of a signal period than the signal itself.
Timing fluctuations in integrated circuit signals are generally referred to as “jitter”. Jitter can be broadly defined in certain interpretations as variation of a signal edge from its ideal position in time, and is an important performance measure for integrated circuit signals, including serial links and clock signals.
Phase noise is another signal performance parameter that is directly related to signal timing jitter. Exemplary references that discuss the one-to-one relationship between phase noise and timing jitter include “Time Domain Analysis and Its Practical Application to the Measurements of Phase Noise of Jitter,” by L. Cosart, L. Peregrino and A. Tambe, as published in IEEE Transaction on Instrumentation and Measurement, Vol. 46, No. 4, August 1977; “Phase Noise and Timing Jitter in Oscillators,” by A. Demir, A. Mehrotra and J. Roychowdhury, as published in IEEE Custom Integrated Circuits Conference, 1998, pp. 45-48; “Jitter and Phase Noise in Ring Oscillators,” by A. Hajimiri, S. Limotyrakis and T. Lee, as published in IEEE Journal of Solid-State Circuits, Vol. 34, No. 6, June 1999; and “An Analytical Formulation of Phase Noise in Signals with Gaussian-distributed Jitter,” by R. Navid, T. Lee and R. Dutton, as published in IEEE Transaction on Circuits and Systems—II: Express Brief, Vol. 52, No. 3, March 2005.
Phase noise is a measure of clock signal purity that is often used in the field of RF circuitry and devices to qualify the impact of oscillator noise on the performance of an RF link. A clock signal may be characterized as having amplitude noise and signal phase variations or phase jitter, both of Which may be due to both random and periodic sources. These noises can result in spreading of signal energy in a wider frequency range and reduction of energy at a given RF carrier frequency. Such spectral spreading negatively affects the quality of communication in an RF link. Spectral spreading due to phase jitter is referred to as phase noise. Oscillators are often qualified with their phase noise characteristics.
The measurement and determination of signal jitter and phase noise, including the various components thereof, is imperative in characterizing the performance of integrated circuits, especially in the production and testing stages of integrated circuit manufacturing. Various devices, including time interval analyzers, counter-based measurement devices, bit-error-rate analyzers, and oscilloscopes, have been developed to measure various signal timing deviations, including jitter.
An example of a time interval analyzer that may be employed to measure high frequency circuit signals and determine various aspects of signal timing deviations is disclosed in U.S. Pat. No. 6,091,671 (Kattan), which is assigned to the present applicants' assignee, Guide Technology, Inc. The time interval analyzer disclosed in Kattan measures jitter, including total cycle-to-cycle jitter, by determining deviations between one or more of the amplitude, phase, and/or pulse width of real signal pulses and ideal signal pulses.
Other examples of time measurement devices that could be configured to measure signal timing variations are disclosed in U.S. Pat. No. 6,194,925 (Kimsal et al.) and U.S. Pat. No. 4,757,452 (Scott et al.) Kimsal et al. discloses a time interval measurement system in which a voltage differential across a hold capacitor generated between events occurring in an input signal determines the time interval between events. Scott et al. provides a system for measuring timing jitter of a tributary data stream that has been multiplexed into a higher-rate multiplex stream using pulse stuffing techniques. Scott et al. is an event counter based system that does not directly measure time intervals but determines their frequency by maintaining a continuous count of the number of pulses occurring within a signal. Still further, U.S. Pat. No. 4,908,784; (Box et al.) discloses a measurement apparatus configured to measure the time interval between two events (start and stop) through counters.
Several measurement devices and methodology for measuring periodic jitter and jitter spectrum are known. One exemplary approach uses an oscilloscope with a high sampling rate and analytical signal method, such as disclosed in “Extraction of Peak-to-peak and RMS Sinusoidal Jitter Using an Analytic Signal Method,” by T. Yamaguchi and M. Soma, as published in IEEE VLSI Test Symposium, 2000, pp. 395-402. Another approach involves an autocorrelation method with high sampling rate oscilloscopes. U.S. Pat. No. 6,898,535 (Draving) discloses a method for determining signal jitter using complete signal edge sampling and Fourier transforms. Additional techniques involve autocorrelation methods with undersampling data sets generated by time interval analyzers. Examples of such techniques are disclosed in “A Method of Serial Data Jitter Analysis Using One-Shot Time Interval Measurements,” by J. Wilstrup, as published at Intl. Test Conference, 1998, pg. 819-823, and in “Jitter Spectrum Analysis Using Time Interval Analyzer (CTIA),” by S. Tabatabaei, Freddy Ben-Zeev and T. Farahmand, as published at Intl. Test Conference, 2005, pg. 198-207. Still further technological examples for measuring periodic jitter and jitter spectrum involve BERT (Bit Error Ratio Testing) methods, such as disclosed in “Jitter Fundamentals: 81250 ParBERT Jitter Injection and Analysis Capabilities,” published by Agilent Technologies as Application Note 5988-9756EN on Jul. 17, 2003. Finally, “Jitter Spectrum Analysis Using Time Interval Analyzer (CTIA)”, by S. Tabatabaei, Freddy Ben-Zeev and T. Farahmand, as published at Intl. Test Conference, 2005, pg. 198-207, discloses a random sampling method with undersampled signal edge timing data.
The BERT method mentioned above typically has very limited dynamic range. The FFT and autocorrelation methods respectively rely on complete signal edge timing information and are typically suitable for use with high sampling rate oscilloscopes. Such methods can be used for characterization applications, but can be costly for production applications.
TIAs and CTIAs lend themselves better for production applications due to efficient edge sampling. However, their sampling rate is typically limited to a few MHz. The autocorrelation and random sampling methods allow periodic jitter and jitter spectrum measurement, but the result does not provide sufficient dynamic range for phase noise measurement.
Although the above examples and others exist for measuring and analyzing various aspects of signal jitter and related performance characteristics including phase noise, no one design exists that encompasses all features and aspects of the present invention.
All the aforementioned patents and other references are incorporated herein by reference for all purposes.